1. Field of the Invention
The present invention relates in general to amusement devices and toys. In particular, the present invention relates to an improved yo-yo which spins freely, upon unwinding, for a predetermined number of rotations.
2. Description of the Related Art
Yo-yos have been known for many years, and continue to enjoy wide popularity. The general components of a yo-yo are a shaft, a rotation body mounted at each end of the shaft and a string mounted to the shaft such that it may be wound upon, and unwound from, the shaft during play. To improve the enjoyment of using a yo-yo it is common for the user to attempt various "tricks" with the yo-yo. Many of these tricks require that the yo-yo spin at the end of the string without winding the string about the shaft, which is commonly referred to as "sleeping".
Sleeping may be achieved by forming a loop at the end of the string through which the shaft extends. The shaft will thus rotate within this loop during sleeping. However, the friction between the loop and the shaft reduces the amount of time the yo-yo sleeps, and wears the string, causing it to break prematurely.
Various yo-yo designs have been proposed to obviate this problem. U.S. Pat. No. 3,175,326 to Isaacson and U.S. Pat. No. 4,895,547 to Amaral both employ a sleeve which may rotate freely about the shaft, with the string attached to the sleeve. This substantially eliminates the wear on the string during sleeping. However, it may be difficult to cause the string to begin rewinding upon the sleeve to return the yo-yo to the user's hand.
A more sophisticated approach is taken in U.S. Pat. No. 4,332,102 to Caffrey. This patent discloses a sleeve on the shaft as in the previously-noted patents, but Caffrey adds a centrifugal clutch between the rotation body and the sleeve. This allows the sleeve to rotate with respect to the shaft above a certain RPM of the rotation body, but fixes the sleeve against relative rotation below this RPM, allowing the yo-yo to be easily retrieved into the user's hand. While this arrangement allows easier rewinding of the string, it often occurs that the clutch release RPM is reached before the string is fully unwound. This results in the remainder of the string unwinding without adding additional torque to the yo-yo, reducing the possible speed of rotation and the duration of the yo-yo's sleep.